4-digits login to Mac like Windows 8

Solution 1:

From - How to Stop Using an iCloud Password to Login to a Mac

1. Go to the  Apple menu and choose “System Preferences”
2. Choose “Users & Groups” and select the primary Mac login that you want to disassociate the iCloud password and use a unique separate password for
3. Click the “Change Password” button next to the user name
4. At the prompt “Do you want to change your iCloud password, or stop using your iCloud password to unlock this Mac and create a separate password?” – choose “Use Separate Password…”
5. Set and confirm the new password and close out of System Preferences when finished